Missing accurate position of the unused import

[adpi2]

Reproduction steps

Scala version: 2.13.8 (also in 2.12.15)
scalacOptions: -Wunused:imports (or -Xlint:_)

package example

import scala.annotation.{nowarn, showAsInfix}

@nowarn
class Example(unusedVar: String)

Problem

The position of the unused import warning spans the entire line: the start column is 0 and the end column is 45. The pointer accurately points to 33, the beginning of the unused import.

This is a problem in LSP because the LSP position only contains the start column and end column, not the pointer. Hence we don't know which import is unused.

Expected result.

The start column should be 33 and end column should be 44.

[SethTisue]

(I've optimistically added the "good first issue" as often improving position information isn't too hard, but it's conceivable that if someone investigated, it would turn out that it isn't so easy to get the specific information to where it's needed in this case.)

[som-snytt]

The position should include just the selector.

I fixed a similar issue IIRC.

[joroKr21]

case class ImportSelector(name: Name, namePos: Int, rename: Name, renamePos: Int) - it's not a tree

[som-snytt]

To remind myself, the similar issue was the "NamePos" business.

The selector not being a tree is a nuisance. I implemented rewrite for unused imports on Scala 3 somehow, on my branch for that, the details of course I have suppressed.